1. Field of the Invention
The field of the invention is reverse osmosis (RO) purification devices. In particular the invention relates to a reverse osmosis purification system which operates on a high ratio of purified water to waste water output.
2. Description of the Prior Art
Reverse osmosis (hereinafter referred to as RO) devices are well known as useful water purification vehicles. Often RO devices have a high ratio of waste water to purified water. In reverse osmosis devices, it is necessary to rinse the surface of the membrane from non-migrating particles to retard buildup of scale which can foul the membrane and require either replacement of the cartridge or costly chemical treatment. In order to reduce scale formation and to retard the buildup of solid materials on the membrane, prior art devices have tended to use a high waste water to purified water ratio to flush non-migrating particles from the membrane. However, such large wastage of water in a ratio of 5 to 1 waste (or brine) to purified water or higher cannot be tolerated in areas where water is at a premium. See e.g., U.S. Pat. No. 4,814,086.
A great variety of organic and inorganic compounds collect on the surface of reverse osmosis membranes from the passage of the contaminated feed streams across the membrane surface. These contaminants when they collect on the membrane reduce the flow of water through the membrane. As a result when the membrane is fouled, the membrane must be either replaced or cleaned.
Chemical cleaning has been used, but it requires flushing the membrane with chemicals which is time consuming and expensive. Ultrasonic energy systems have been proposed to vibrate the fluid and thereby clean the membranes. Care must be taken in ultrasonic cleaning of the membrane not to destroy the membrane from the wave vibrations. The use of ultrasonic cleaning transducers however, significantly increase the complexity of the device. U.S. Pat. No. 4,253,962 is an example of an reverse osmosis system containing a ultrasonic vibratory cleaning system.
Flow controllers which allow controlled volume of water flow are known for use as emitters in irrigation. See for example, U.S. Pat. No. 4,869,432.